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AQ Monitoring Results: Elemental Carbon in Boyle Heights

This page last reviewed September 02, 2010

Background

Elemental carbon consists of tiny black solid particles of soot, most of which are smaller than 2.5 microns. This small size allows the pollutant to reach deep in the lungs, where they may be deposited to result in adverse health effects.

Elemental carbon was collected with the possibility of using elemental carbon as a surrogate for diesel particulate matter. The terms elemental carbon (EC), black carbon (BC) and "soot" are often used by atmospheric researchers to designate products of incomplete combustion that contain randomly oriented graphitic structures interspersed with other compounds. Elemental carbon was considered a good surrogate for diesel particulate matter because of the relatively high fraction of elemental carbon in diesel particle matter and the relatively high particulate matter emissions from diesel-powered vehicles, compared to gasoline-powered vehicles. Some studies imply a correspondence
between elemental carbon measurements and diesel PM related to large truck traffic. But as diesel technologies
improved and the diesel fleet became cleaner, it became more difficult to use elemental carbon alone as the marker
for diesel particulate matter. Since other sources of elemental carbon became more significant as emissions from
the diesel fleet decreased, this increased the uncertainty associated with the diesel particulate matter estimates
based on elemental carbon. Other combustion processes such as fireplaces, cooking, forest fires, gasoline engines,
agricultural burning, and power plants also emit elemental carbon.

Elemental carbon in the atmosphere exerts a warming effect similar to that of Greenhouse Gases. Thus, control of
elemental carbon emissions has been proposed as a strategy to mitigate global warming, while at the same time being
beneficial from the point of view of human health effects from particulate matter.

Ambient Monitoring Results

Elemental carbon is not routinely monitored, and earlier studies of elemental carbon used different analysis methods, so there are no comparable regional or statewide values provided. Below, we provide graphs of elemental carbon measurements at Hollenbeck, Science Center, and Soto Street and many of the observations are below the limit
of detection.

Cancer Risk

While diesel particulate matter significantly contributes to overall risk from toxic air contaminants, it has proved very elusive to measure. We are exploring the options to estimate the impact of diesel particulate matter on public
health in the community, including using elemental carbon as a surrogate.